This invention relates to a catalytic system for polymerizing olefins, a novel component of the system containing titanium halide, a process for preparing the novel component containing titanium halide, and the use of the system in polymerizing olefins, especially propylene.
The polymerization of olefins by coordinate complex catalytic systems, often termed Ziegler-Natta catalysis, has been well-known for over 25 years. Generally, there are two components in this type of system: one based on an organoaluminum compound or its substitute, the other containing a titanium or other transition metal halide. Although thousands of such catalytic systems have been disclosed, there is always a quest for improvement in two important properties: activity and isotactic index.
Activity is measured by the grams of polyolefin produced per gram of titanium component or other transition metal component employed in the catalytic system. The higher the activity, the lower the amount of metallic ash and corrosive halide left in the polymer. If the activity is high enough, e.g. .gtoreq.3,000, then the de-ashing step in processing the final polyolefin can be omitted--an important improvement.
For olefins, such as propylene, which can form isotactic structures, the higher the isotactic index, the better the physical properties of the polymer. Isotactic polypropylene is more ordered, less soluble in halocarbons or hydrocarbons, and useful for its higher strength than the more soluble atactic form. Isotactic indices of 93 or higher are favored for commercial polypropylene. ;p Previously Kashiwa et al. disclosed in U.S. Pat. No. 3,642,746 a process for polymerizing olefins by means of a catalytic component supported on a metal dihalide, which had been treated with an electron-donor compound and then reacted with either titanium tetrachloride or vanadium tetra- or pentachloride. Among the electron-donor compounds are aliphatic and cyclic ethers.
Yamaguchi et al. disclose in U.S. Pat. No. 3,989,881 a component used for polymerizing olefins comprising a solid ethereal complex of magnesium halide and titanium/vanadium halide, which may be obtained by milling the ethereal complexes of magnesium halide and the transition metal halide.
Hirota et al. disclose in U.S. Pat. No. 4,180,636 a copulverized polymerization component obtained by milling a magnesium halide support with an aromatic additive, a mixture of titanium tetrahalide and an electron donor, which may be an ether, plus an organo-aluminum compound activated by an aromatic carboxylic ester.
Wagner discloses in U.S. Pat. No. 4,186,107 a coordinate complex polymerization catalyst employing a component of titanium halide on a magnesium chloride support, prepared by the reduction of a magnesium alkyl with an aluminum alkyl halide followed by optional post treatment with a dialkyl ether.
Sunada et al. in Belgian published patent application No. 880,807 of Apr. 17, 1980 based on Japanese patent application No. 79/152,818 of Nov. 26, 1979 (see C.A., Vol. 93, 240287N) disclose a component for a polymerization catalyst prepared by heating titanium tetrachloride, an ether, and an organoaluminum compound in an aliphatic hydrocarbon solvent containing a haloarene, cooling the mixture below 40.degree. C., adding an ether plus titanium tetrachloride then heating the solution, and then repeating the cooling/heating cycle one or more times with repeated additions of both ether and titanium tetrachloride.
All five of the disclosures above are incorporated by reference into this application.
It is an object of this invention to provide a catalytic system for polymerizing olefins, such as propylene, so that de-ashing may be omitted and product with high isotactic index prepared. Other objects of the present invention will be apparent to those skilled in the art.